a) Field of the Invention
This invention relates to a photographing apparatus for microscopes which enables switching and simultaneous observations on a fluorescent sample by using transmitted and reflected illumination light.
b) Description of the Prior Art
In microscopes, the observation of a cell for a fluorescent sample has been made using reflected fluorescence in the past. With this fluorescence observation only, however, it is hard to find where the area of the cell emitting fluorescence is located in relation to the entire sample. Thus, in order to confirm the area of the cell emitting fluorescence which is hard to be recognized from the fluorescence observation while viewing the entire profile of the sample, phase-contrast and differential interference contrast observations making use of transmitted illumination light has come to be employed in combination with the reflected fluorescence observation so as to carry out a switching observation in which the transmitted illumination and reflected fluorescence observations are switched to each other or a simultaneous observation which is made by overlapping a reflected fluorescence image with a transmitted illumination image.
For the simultaneous observation on the reflected fluorescence and transmitted illumination images, the reflected fluorescence image, which is darker, needs the balance of brightness to be adjusted in comparison with a phase-contrast or differential interference contrast image formed by transmitted illumination light. Further, it also needs a very fine adjustment for the optimum simultaneous observation.
In the past, the adjustment of brightness of an image to be observed has been made by controlling the voltage of the light source for a transmitted illumination system or inserting an ND filter whenever the sample, microscopy, or the magnification of an objective lens is changed.
An example of the microscope equipped with such a light-adjusting means is set forth in Japanese Patent Preliminary Publication No. Sho 54-71652. Referring now to FIG. 1 showing a fundamental optical system of this microscope, illumination light emitted from a light source 1 for transmitted illumination, such as a halogen lamp or a tungsten lamp, is collected by a collector lens 2 and, after passing through a relay lens 3 and being reflected upward from a reflecting mirror 4, illuminates a sample 6 through a condenser lens 5. A transmitted image of the sample formed by the illumination light is magnified by an objective lens 7 and inclined at an angle easy of observation by an inclined prism 8 for splitting light to be observed through an eyepiece 9. Further, while split light traveling in a straight line from the inclined prism 8 is imaged on a film plane 10 for photography, part of the light split by a half mirror 11 on the way to the film plane 10 is conducted to a light-detecting element 12 for detecting the amount of light.
The amount of light detected by the light-detecting element 12 is compared with a preset level and thus the amount of light of the light source 1 is altered by a light-adjusting device 13. It follows from this that the sample image can be observed with the optimum amount of light according to, for example, the switchover of the objective lens.
Also, apparatus designed so that the amount of light of the light source for illumination light is adjusted, independently of the light-detecting element, according to the switchover of the objective lens, are described by Japanese Patent Preliminary Publication No. Sho 59-172618 and Japanese Utility Model Preliminary Publication No. Sho 61-185025.
Light-adjusting means proposed by Japanese Patent Publication No. Sho 60-37538 and Japanese Utility Model Preliminary Publication No. Sho 63-19810 are such that the illuminance of the image plane of illumination light is detected by the light-detecting element, such as a photoelectric converter, and the adjustment of the amount of light is made, according to the output of the light-detecting element, by an optical attenuator, such as a filter, disposed in an optical path for transmitted illumination. Similarly, the apparatus set forth in Japanese Patent Preliminary Publication No. Sho 59-172617 is adapted to adjust the amount of light in accordance with the switchover of the objective lens, using the optical attenuator.
Any of the foregoing prior art, however, is such that the amount of transmitted illumination light is changed by measuring the amount of light of the transmitted illumination image or according to the switchover of the objective lens while the sample is illuminated, or shows such an automatic light-adjusting means that the amount of reflected illumination light is changed by measuring the amount of light of the reflected fluorescence image. In any case, the prior art is designed so that the amount of illumination light is adjusted in such a manner that only when observations are made using one illumination light, the amount of light of the sample image formed by the illumination light is measured, thus enabling observations to be made with the optimum amount of light.
Hence, in the simultaneous observation on the reflected fluorescence and transmitted illumination images, the balance of brightness has been adjusted in such a way that an observer, while viewing the sample image, controls the voltage of the light source of the transmitted illumination system or inserts the ND filter into the optical path for transmitted illumination.
To position the sample and specify the area emitting fluorescence in making observations, however, a observation mode is frequently switched from the reflected fluorescence observation to the simultaneous observation or from the transmitted illumination observation (phase-contrast or differential interference contrast observation) to the simultaneous observation, and whenever the switchover is performed, the observer must adjust the brightness while viewing the sample image. This makes the operation of the microscope complicated. In addition, since in the reflected fluorescence observation the fluorescent staining of the sample is subject to bleaching due to excited light, it is important to reduce the time of irradiating the sample with the excited light, but there is the difficulty that such adjustment of the balance of brightness is so delicate that much time is required therefor.